Establishing a telecommunications connection in a mobile communication system

Abstract

A method, a mobile communication system and a mobile station for establishing a telecommunication connection on a direct mode channel and for improving radio coverage by way of using a simple and cheap repeater. An inexpensive and simple repeater is achieved by, instead of using two transceivers, using two receivers and just one transmitter. A mobile station, prepared for direct mode communication, is able to switch between channels answering to commands sent from the repeater.

I claim: 
     
       1. A method for establishing a telecommunications connection in a mobile communication system which has a base station, a plurality of mobile stations arranged for communicating with the base station at a respective uplink frequency and a respective downlink frequency of respective control and traffic channels of the base station, at least a first and a second mobile station arranged for communicating on a direct mode channel that comprises an uplink channel and a downlink channel, these first and second mobile stations arranged for communicating on the direct mode channel having respective memories, a repeater station arranged to relay traffic between the mobile stations arranged for communicating on the direct mode channel and the base station; comprising the steps of: the repeater station listening to a downlink frequency of a control channel of the base station and the uplink channel of the direct mode channel;   a first said mobile station arranged for communicating on said direct mode channel sending a call set-up request to the repeater station on the uplink channel of the direct mode channel;   the repeater station transmitting the call set-up request to the base station;   in response to receiving the call set-up request, the base station commanding the repeater station to move to a specific traffic channel from any said traffic channels of the base station;   the repeater station using the downlink channel of the direct mode channel to command the mobile stations arranged for communicating on the direct mode channel, via a command, to switch-over to the uplink frequency of said specific traffic channel and start listening to said specific traffic channel;   the repeater station moving itself to the downlink frequency of said specific traffic channel and starting to listen to said specific traffic channel;   in response to receiving said command of the repeater station, said first and second mobile stations arranged for communicating on the direct mode channel storing information about said specific traffic channel in the respective memories thereof and moving to the uplink channel of the direct mode channel for sending a transmission to the repeater station and to the uplink frequency of said specific traffic channel for listening to transmissions forwarded by the repeater station;   the repeater station forwarding a transmission received from the base station to said first and second mobile stations at the uplink frequency of said specific traffic channel; and   the repeater station using the uplink frequency of said specific traffic channel to forward transmissions transmitted by said first and second mobile stations on the direct mode channel, to the base station and to said mobile stations which are listening to the uplink frequency of said specific traffic channel.   
     
     
       2. A method according to claim 1, wherein: having received the command of the repeater station to move to the uplink frequency of said specific traffic channel and start listening to said specific traffic channel, a respective said mobile station adding information about said specific traffic channel to a transmission of said respective mobile station, upon sending this transmission on the uplink channel of the direct mode channel, and, in response to receiving said information about said specific traffic channel a third mobile station, having later tuned to the uplink channel of the direct mode channel, moving to the uplink frequency of said specific traffic channel, starting to listen to said specific traffic channel.   
     
     
       3. A method according to claim 1, wherein: the repeater station, in forwarding said transmission received from the base station at the uplink frequency of said specific traffic channel, adding an identifier of said repeater station to the respective said transmission of the base station, and on the basis of the identifier of said repeater station the base station becoming knowledgeable that a respective transmission received by the base station at the uplink frequency of said specific traffic channel comes from the repeater station, and, in response to thereby becoming knowledgeable, the base station not forwarding the respective said transmission to said mobile communication system.   
     
     
       4. A method according to claim 1, wherein: the repeater station, in response to receiving a transmission sent by the base station, forming a new transmission by adding thereto an identifier that contains information about direct mode transmission and a transmission received from said first mobile station on the direct mode channel, and sending said new transmission at the uplink frequency of said specific traffic channel to the base station for forwarding to said mobile communication.   
     
     
       5. A method according to claim 1, further comprising: the repeater station, in terminating a transmission at the uplink frequency of said specific traffic channel, sending a command at the uplink frequency of said specific traffic channel to said mobile stations arranged for communicating on said direct mode channel, instructing these mobile stations to move to the direct mode channel and to start listening to said direct mode channel.   
     
     
       6. A method for establishing a telecommunications connection in a mobile communication system which has a base station, a plurality of mobile stations arranged for communicating with the base station at a respective uplink frequency and a respective downlink frequency of respective control and traffic channels of the base station, at least a first and a second mobile station arranged for communicating on a direct mode channel that comprises an uplink channel and a downlink channel, a repeater station arranged to relay traffic between the mobile stations arranged for communicating on the direct mode channel and the base station, comprising the steps of: the repeater station listening to a downlink frequency of a control channel of the base station and the uplink channel of the direct mode channel;   the base station sending a call set-up request, for setting up a call to be established, to the repeater station, requesting at least said first mobile station to participate in the call to be established and notifying the repeater station of a specific traffic channel allocated for the call from among said traffic channels of the base station;   the repeater station using the downlink channel of the direct mode channel to command said mobile stations arranged for communicating on the direct mode channel, via a command, to switch over to the uplink frequency of said specific traffic channel and to start listening to said specific traffic channel;   said repeater station moving itself to the downlink frequency of said specific traffic channel, starting to listen to said specific traffic channel;   in response to receiving said command of the repeater station, said first and second mobile stations arranged for communicating on the direct mode channel storing information about said specific traffic channel in the respective memories thereof and moving to the uplink channel of the direct mode channel for sending a transmission to the repeater station and to the uplink frequency of said specific traffic channel for listening to transmissions forwarded by the repeater station;   the repeater station forwarding a transmission received from the base station to said first and second mobile stations at the uplink frequency of said specific traffic channel;   the repeater station using the uplink frequency of said specific traffic channel to forward transmissions transmitted by said first and second mobile stations on the direct mode channel, to the base station and to said mobile stations which are listening to the uplink frequency of said specific traffic channel.   
     
     
       7. A method according to claim 6, wherein: having received the command of the repeater station to move to the uplink frequency of said specific traffic channel and start listening to said specific traffic channel, a respective said mobile station adding information about said specific traffic channel to transmission of said respective mobile station upon sending this transmission on the uplink channel of the direct mode channel, and, in response to receiving said information about said specific traffic channel, a third mobile station, having later tuned to the uplink channel of the direct mode channel, moving to the uplink frequency of said specific traffic channel, starting to listening to said specific traffic channel.   
     
     
       8. A method according to claim 6, wherein: the repeater station, in forwarding said transmission received from the base station at the uplink frequency of said specific traffic channel, adding an identifier of said repeater station to the respective said transmission of the base station, and one the basis of the identifier of said repeater station the base station becoming knowledgeable that a respective transmission received at the uplink frequency of said specific traffic channel comes from the repeater station, and, in response to thereby becoming knowledgeable, the base station not forwarding the respective said transmission to said mobile communication system.   
     
     
       9. A method according to claim 6, wherein: the repeater station, in response to receiving a transmission sent by the base station, forming a new transmission by adding thereto an identifier that contains information about direct mode transmission and a transmission received from said first mobile station on the direct mode channel, and sending said new transmission at the uplink frequency of said specific traffic channel to said base station for forwarding to said mobile communication system.   
     
     
       10. A method according to claim 6, further comprising: the repeater station, in terminating a transmission at the uplink frequency of said specific traffic channel, sending a command at the uplink frequency of said specific traffic channel to said mobile stations arranged for communicating on said direct mode channel, instructing these mobile station to move to the direct mode channel and to start listening to said direct mode channel.   
     
     
       11. A mobile communication system comprising: a base station having control and traffic channels each comprising an uplink frequency and a downlink frequency;   at least a first and a second mobile station arranged for communicating on a direct mode channel that comprises an uplink channel and a downlink channel; and   a repeater station arranged for transmitting traffic between the mobile stations communicating on the direct mode channel and the base station;   the repeater station comprising: a first receiver unit arranged for receiving radio messages from the base station;   a second receiver unit arranged for receiving radio messages from mobile stations communicating on the uplink frequency of the direct mode channel;   a control unit arranged for controlling the operation of said first and second receiver units and the repeater station, and     only a single transmitter unit, arranged for transmitting radio messages in response to commands of said control unit, to the base station and a mobile station listening to an uplink frequency of a traffic channel of the base station, or to a mobile station from among said mobile stations arranged communicating on the direct mode channel.   
     
     
       12. A mobile communication system according to claim 11, wherein the repeater station further comprises: means for forwarding to the base station a call set-up request transmitted by a said mobile station communicating on the direct mode channel, the repeater station being arranged to be commanded, in response to receipt by the base station of the call set-up request, to move to a specific said traffic channel.   
     
     
       13. A mobile communication system according to claim 12, wherein the repeater station further comprises: means for commanding the mobile stations communicating on the direct mode channel to switch over to the uplink frequency of said specific traffic channel to listen to the transmissions of the repeater station;   means for moving the repeater station to the downlink frequency of said specific traffic channel to listen to said specific traffic channel;   means for moving the repeater station to the uplink channel of the direct mode channel to listen to said uplink channel; and   a switch for switching the repeater station to transmit either on the downlink channel of the direct mode channel or at the uplink frequency of said specific traffic channel, for sending a downlink transmission of the traffic channel as an uplink transmission of the traffic channel, and for adding a transmission received on the uplink channel of the direct mode channel to an uplink transmission of said specific traffic channel as sent by the repeater station.   
     
     
       14. A mobile communication system according to claim 11, wherein the repeater station further comprises: means for commanding the mobile stations communicating on the direct mode channel to switch over to the uplink frequency of a specific said traffic channel to listen to the transmissions of the repeater station;   means for moving the repeater station to the downlink frequency of said specific traffic channel to listen to said specific traffic channel;   means for moving the repeater station to the uplink channel of the direct mode channel to listen to said uplink channel; and   a switch for switching the repeater station to transmit either on the downlink channel of the direct mode channel or at the uplink frequency of said specific traffic channel, for sending a downlink transmission of the traffic channel as an uplink transmission of the traffic channel, and for adding a transmission received on the uplink channel of the direct mode channel to an uplink transmission on said specific traffic channel as sent by the repeater station.   
     
     
       15. A mobile station adapted to communicate with another mobile station and with a repeater station on a direct mode channel having an uplink channel and a downlink channel, the repeater station further arranged to communicate with a base station on a traffic channel having an uplink frequency and a downlink frequency, said mobile station comprising: a memory;   a transceiver, capable of communicating on the direct mode channel;   a controller for controlling the operation of said mobile station;   switching means, which are arranged to be responsive to a command sent by the repeater station, for moving said transceiver of said mobile station to listen to a repeater station transmission on an uplink frequency of a traffic channel specified in said command sent by said repeater station, the repeater station transmission on said uplink frequency of said traffic channel including a relay of a signal received by said repeater station from said base station on said downlink frequency of said traffic channel.   
     
     
       16. A mobile station according to claim 15, further comprising: means for containing information about said specific traffic channel in a transmission of the mobile station, so that in response to receiving said transmission of said mobile station and said information contained therein, any third mobile stations that later tune to the uplink channel of the direct mode channel will be caused to switch over to the uplink frequency of said specific traffic channel and to start to listen to said specific traffic channel.